This paper deals with the results so obtained after conducting exhaustive experimentation on 1 & 3-sides concave dimple roughened SAH in terms of Nusselt number (Nu) & friction factor (f). The geometrical & flow parameters were used as dimensionless ratio as relative dimple pitch (p/e), relative dimple height (e/Dh), relative dimple depth (e/d) and ‘Re’ in the range of 8-15, 0.018-0.045, 1-2 and 2500-13500 respectively. For various sets of roughness parameters, there exists an optimum roughness parameter, either side of which heat transfer rate decreased. The optimum roughness parameters found under present investigation is p/e=12, e/Dh=0.036 and e/d=1.5. The maximum rise in ‘Nu’ for varying ‘p/e’, ‘e/Dh’ & ‘e/d’ was respectively found to be of the order of 2.6 to 3.55 times, 1.91 to 3.42 times and 3.09 to 3.94 times than one side concave dimple roughened duct for the parameters range investigated. The maximum rise in friction factor of 3-sides concave dimple over those of 1-side roughened ones for varying ‘p/e’, ‘e/Dh’ & ‘e/d’ was respectively found to be as 1.62 to 2.79 times, 1.52 to 2.34 times and 2.21 to 2.56 times
concave dimple, relative dimple pitch, relative dimple height, relative dimple depth, nusselt number,; friction factor
Ahn S. W. (2001). The eﬀect of roughness types on friction factor and heat rectangular duct. Int Commun Heat Mass Transf., Vol. 28, pp. 933-942. http://dx.doi.org/10.1016/s0735-1933(01)00297-4
Akhtar N., Mullick S.C. (2012). Effect of absorption of solar radiation in glass-cover(s) on heat transfer coefficients in upward heat flow in single and double glazed flat-plate collectors. International Journal of Heat and Mass Transfer, Vol. 55, No. 1-3, pp. 125-132. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2011.08.048
Armaroli N., Balzani V. (2016). Solar Electricity and Solar Fuels: Status and Perspectives in the Context of the Energy Transition. Chemistry-A European Journal, Vol. 22, pp. 32-57. http://dx.doi.org/10.1002/chin.201611269
ASHRAE Standard 93-97 (1977). Methods of testing to determine the thermal performance of solar collectors. American Society of Heating, Refrigerating and Air-conditioning Engineers Inc., Atlanta Ga.
Bhagoria J. S., Saini J. S., Solanki S. C. (2002). Heat transfer co-efficient and friction factor correlation for rectangular solar air heater duct having transverse wedge shaped rib roughness on the absorber plate. Renewable Energy, Vol. 25, pp. 341-369. http://dx.doi.org/10.1016/s0960-1481(01)00057-x
Chang S. W., Liou T. M., Chiang K. F., Hong G. F. (2008). Heat transfer and pressure drop in rectangular channel with compound roughness of V-shaped ribs and deepened scales. International Journal of Heat Mass Transfer, Vol. 51, pp. 457-468. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2007.05.010
Dippreyy D. F., Sabersky R. H. (1963). Heat and momentum transfer in smooth and rough tubes at various Prandtl numbers. Int J Heat Mass Transf., Vol. 6, pp. 329-53. http://dx.doi.org/10.1016/0017-9310(63)90097-8
Duffie J. A., Beckman W. A. (1991). Solar Engineering Thermal Processes, John Wiley, New York.
Edwards F. J., Sheriﬀ N. (1961). The heat transfer and friction characteristics for forced convection air ﬂow over a particular type of rough surface. Int Dev Heat Transf. ASME, pp. 415-425.
Firth R. J., Meyer L. (1983). A comparison of the heat transfer and friction factor performance of four different types of artiﬁcially roughened surface. Int J Heat Mass Transf., Vol. 26, No. 2, pp. 175-83. http://dx.doi.org/10.1016/s0017-9310(83)80024-6
Gupta D., Solanki S. C., Saini J. S. (1997). Thermohydraulic performance of solar air heaters with roughened absorber plates. Solar Energy, Vol. 61, pp. 33-42. http://dx.doi.org/10.1016/s0038-092x(97)00005-4
Han J. C., Park J. S., Lei C. K. (1985). Heat transfer enhancement in channel with turbulence promoters. ASME Journal Engineering for Gas Turbine and Power, Vol. 107, pp. 628-635. http://dx.doi.org/10.1115/1.3239782
Han J. C., Zhang Y. M., Lee C. P. (1991). Augmented heat transfer in square channels with parallel, crossed, and V shaped angled ribs. ASME Journal of Heat Transfer, Vol. 113, pp. 590-596. http://dx.doi.org/10.1115/1.2910606
Karwa R., Solanki S., Saini J. (2001). Thermo-hydraulic performance of solar air heaters having integral chamfered rib roughness on absorber plates. Energy, Vol. 26, No. 2, pp. 161-176. http://dx.doi.org/10.1016/S0360-5442(00)00062-1
Kline S. J., Mcclintock F. A. (1953). Describing uncertainties in single sample experiments. Mech Eng., Vol. 75, pp. 3-8.
Naphon P. (2008). Effect of corrugated plates in an in-phase arrangement on the heat transfer and flow developments. International Journal of Heat Mass Transfer, Vol. 51, pp. 3963-3971. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2007.11.050
Nguyen T. M., Khodadadi J. M., Vlachos N. S. (1989). Laminar ﬂow and conjugate heat transfer in rib roughened tubes. Numerical Heat Transfer Applications, Vol. 15, pp. 165-79. http://dx.doi.org/10.1080/10407788908944683
Patil A. K., Saini J. S., Kumar K. (2012). Heat transfer and friction characteristics of solar air heater duct roughened by discrete V-shape ribs combined with staggered rib piece. J Renew Sustain Energy, Vol. 4, pp. 13115. http://dx.doi.org/10.1063/1.3682072
Pillar P. K., Agarwal R. C. (1981). Factors influencing solar energy collector efficiency. Applied Energy, Vol. 8, pp. 205-213. http://dx.doi.org/10.1016/0306-2619(81)90018-0
Prasad B. N., Saini J. S. (1988). Effect of artificial roughness on heat transfer and friction factor in a solar air heater. Solar Energy, Vol. 41, No. 6, pp. 555-560. http://dx.doi.org/10.1016/0038-092X(88)90058-8
Prasad K., Mullick S. C. (1985). Heat transfer characteristics of a solar air heater used for drying purposes. Applied Energy, Vol. 13, pp. 83-93. http://dx.doi.org/10.1016/0306-2619(83)90001-6
Saini R. P., Verma J. (2008). Heat transfer and friction correlations for a duct having dimple shape artificial roughness for solar air heater. Energy, Vol. 33, pp. 1277-1287. http://dx.doi.org/10.1016/j.energy.2008.02.017
Singh S., Chander S., Saini J. S. (2012). Investigations on thermo-hydraulic performance due to ﬂow-attack-angle in V-down rib with gap in a rectangular duct of solar air heater. Appl Energy, Vol. 97, pp. 907-912. http://dx.doi.org/10.1016/j.apenergy.2011.11.090
Singh S., Chander S., Saini J. S. (2015). Thermo-hydraulic performance due to relative roughness pitch in V-down rib with gap in solar air heater duct-Comparison with similar rib roughness geometries. Renewable and Sustainable Energy Reviews, Vol. 43, pp. 1159-1166. http://dx.doi.org/10.1016/j.rser.2014.11.087
Skullong S., Promvonge P. (2014). Experimental Investigation on Turbulent Convection in Solar Air Heater Channel Fitted with Delta Winglet Vortex Generator. Chinese Journal of Chemical Engineering, Vol. 22, No. 1, pp. 1-10. http://dx.doi.org/10.1016/S1004-9541(14)60030-6
Sukhatme S. P. (1986). Solar Energy Engineering, Prentice Hall Inc., New Jersey.
Varun Saini, R. P. Singal S. K. (2007). A review of roughness geometry used in solar air heaters. Sol Energy, Vol. 81, pp. 1340-50. http://dx.doi.org/10.1016/j.solener.2007.01.017
Yadav A. S., Bhagoria J. L. (2014). A CFD based thermo-hydraulic performance analysis of an artiﬁcially roughened solar air heater having equilateral triangular sectioned rib roughness on the absorber plate. International Journal of Heat and Mass Transfer, Vol. 70, pp. 1016-1039. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.11.074